Illuminated indication device for road traffic

ABSTRACT

An illuminated indication device for road traffic. A number of indicating points are formed with indicating lenses in or on an indicating surface. The indicating lenses have a light entry surface and a light exit surface and are illuminated by the rear face of the indicating surface, which has individually allocated light-emitting elements with a small diameter. One object of this invention is to make the indication device easier to read. The light entry surface and/or the light exit surface is shaped in such a way that the distribution of light intensity on the indicator surface extends further in a horizontal direction than in a vertical direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an illuminated display device for roadtraffic, wherein a plurality of display points with display lenses,which have a light inlet surface and a light outlet surface and areilluminated from a direction of a back of the display surface byrespectively associated illumination elements of lesser diameter, areformed in or on a display surface, and wherein a light inlet surfaceand/or a light outlet surface each is shaped so that the light intensitydistribution on the display side has a greater extension in thehorizontal direction than in the vertical direction.

2. Description of Related Art

An illuminated display device of this type is disclosed in U.S. Pat. No.4,113,347. In this known illuminated display device a lateral increaseof the angle of radiation, or respectively of the light intensitydistribution is achieved with two lens elements embodied next to eachother.

Japanese Patent Reference JP-A 03 054 592 discloses arranging thecylinder axes of two cylindrical lenses of different curvaturesperpendicularly with respect to each other for achieving a greaterextension of the light intensity distribution in one direction over theother.

A further illuminated display device is disclosed by German PatentReference DE 40 40 467 C1. In this known illuminated display device aplurality of display points are formed on a display surface byrespective display lenses, which are illuminated from a back of thedisplay surface by illuminating elements in the form of optical fibersdirected on the display lenses. Display points with relatively largesurfaces, which improve the visibility of a displayed character, areachieved with the display lenses, whose diameter is greater than thediameter of the optical fibers. In order to achieve a sufficiently highillumination density, the light emission is bundled with the lenses, butit is possible for the illumination density to become too low for goodvisibility at greater angles outside of the radiating axis, inparticular in case of lighter surroundings.

SUMMARY OF THE INVENTION

One object of this invention is to provide an illuminated display deviceof the type mentioned above, wherein an increased illumination densityof the light points at increased observation angles is achieved, whilethe light output of the illuminating elements remains unchanged, whereinthe embodiment is also advantageous for maintenance purposes.

This object is achieved with a light outlet surface and/or a light inletsurface formed so that the light intensity distribution on the displayside is greater in the horizontal direction than in the verticaldirection. An increased light intensity or illumination density of thedisplay points under increased horizontal observation angles resultsfrom this design of the display lenses, so that the visibility of thedisplay is assured, even when approached from a curve in the road, forexample. Although the distribution of the light intensity in thevertical direction is reduced to a correspondingly lesser angle withrespect to the radiating axis at the expense of the light intensitydistribution in the horizontal direction, it is sufficient for achievingrequirements for good readability from the customary observationdistances. The light from the display as a whole is considerablyimproved for actual observation conditions in road traffic.

The further measures are also particularly advantageous for maintenancebecause the display lens has a cylindrical section adjoining the lightinlet surface, and on its radially symmetrical light inlet surfacetapers toward an exterior in the form of a section of a cone, and has acentral concave section. It is sufficient if the display lens isdesigned radially symmetrical at least in the light inlet area.

A suitable embodiment of the illuminated display device for goodvisibility consists in that the half-width value of the light intensitydistribution in the horizontal direction is greater by at least a factorof 1.4 than the half-width value in the vertical direction. For example,the half-width value in the horizontal direction can be twice as greatas in the vertical direction, whereas within the half-width value thelight intensities with the same light sources is just as great as withinthe half-width value of light intensity distributions of customaryradially symmetrical light intensity distributions. If up to now thehalf-width value of a radially symmetrical light intensity distributionwas 12°, for example, this light intensity distribution is achieved withthe present display device within a vertical half-width value of 6°, forexample, and a horizontal half-width value of 24°, so that doubling ofthe corresponding extra-axial recognition angle results in the importanthorizontal range.

One embodiment of the display lenses has a radius of curvature of thelight outlet surface which is less in the horizontal direction than inthe vertical direction, wherein in another embodiment the light outletsurface is curved convexly toward the outside in the vertical directionand has a curvature radius of zero in the horizontal direction.

For production and mounting, the display lenses is designed so that thelight outlet surface is formed in the shape of a section of a cylinder.Because of the cylindrical shape it is possible, for example, to producethe lenses from a glass rod made of an acrylic material and to insert acylindrical piece into a corresponding bore in the display surface andfix it in place there.

A defined positioning and contact, as well as a tight securingpossibility against the display surface, is achieved because the displaylens has a flange-like collar on the circumference which rests on theoutside of the display surface.

One step is advantageous for simple positioning of the display lenses inthe circumferential direction, wherein a marker for the installedposition is formed on the collar, In this case, a simple positioning aidincludes the marker designed as a section of a circle.

With the above embodiments it is also possible to exchange the inletsurface with the outlet surface by rotating the lens by 180°.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will be explained in greater detail in view of anembodiment and by referring to the drawings, wherein:

FIG. 1 is a top view of a display lens, according to one preferredembodiment of this invention;

FIG. 2 is a side view of the display lens shown in FIG. 1; and

FIG. 3 is a front view of the display lens shown in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

A display lens 1 is shown in the drawings at FIG. 1 in a plan view, adisplay lens from the side at FIG. 2, and at FIG. 3 from the directionof a light inlet surface 9.

In a direction of the optical axis, the display lens 1 has a cylindricalsection 2, which is adjoined at the one side by the light inlet surface9 facing a display surface, and on the other side by a light outletsurface 8, illuminated by an associated illuminating element, forexample an optical fiber or a light-emitting diode, which is illuminatedon its side facing away from the display surface 1.

The light outlet surface 8 is formed in a cylinder shape, wherein itextends convexly curved toward the outside in the vertical direction,such as shown by reference numeral 4, and straight in the horizontaldirection, such as shown by reference numeral 3.

The light inlet surface 9 comprises a slope 7 in the shape of a sectionof a cone on the circumference, which is cut off in the shape of asection of a circle on its side which is downwardly oriented in theinstalled position, as shown in FIG. 3 in particular. Moreover, asection 5 in the shape of a section of a sphere is formed in a centralarea of the light inlet surface 9. In the direction toward the lightoutlet surface 8, the light inlet surface 9 has a shoulder-like collar 6on the outer circumference of the cylindrical section 2, by which thedisplay lens rests in a flange-like manner against the display surfacein the assembled state, so that a defined installed position in theaxial direction is achieved. In the circumferential direction, a definedinstalled position is formed by a marker, such as a cut-off portion 10,on an underside of the rim of the light inlet surface 9, which extendsin the axial direction over the collar 6 and which, in an axial planview as shown in FIG. 3, tangentially adjoins the cylindrical section 2,so that the entry of the light or the exit of the light is not thushampered.

The display lens 1 embodied in the described manner results in awidening of the light intensity distribution curve in the horizontaldirection and a narrowing of the light intensity distribution curve inthe vertical direction, wherein the half-width value can be 6° in thevertical direction and 24° in the horizontal direction, for example. Inthis case the light intensity within the half-width value is as great aswith a radially symmetrical light intensity distribution with ahalf-width value of 12°, if the radiation into the display lens 1 is thesame. The described embodiment of the lens 1 is also advantageous forits mounting and production.

What is claimed is:
 1. In an illuminated display device for roadtraffic, the display device comprising a plurality of display pointsdefined by a plurality of display lenses (1), each of the display lenseshave a light inlet surface (9) and a light outlet surface (8) and areilluminated from a direction of a back of a display surface byrespectively associated illumination elements of lesser diameter, thedisplay lenses are formed one of in and on the display surface, andwherein a light intensity distribution on a display side of the displaydevice is greater in a horizontal direction than in a verticaldirection, the improvement comprising: each of the display lenses (1)having a cylindrical section (2) adjoining the light outlet surface (8)and the light inlet surface (9) of each of the display lenses (1) havinga central concave section (5) surrounded by a slope surface (7) in ashape of a section of a cone which tapers toward an exterior of thedisplay lens (1).
 2. In the illuminated display device in accordancewith claim 1, wherein a first half-width value of a light intensitydistribution in the horizontal direction is greater by at least a factorof 1.4 than a second half-width value in the vertical direction.
 3. Inthe illuminated display device in accordance with claim 2, wherein aradius of curvature of the light outlet surface (8) is less in thehorizontal direction than in the vertical direction.
 4. In theilluminated display device in accordance with claim 3, wherein the lightoutlet surface (8) is curved convexly toward an outside in the verticaldirection and has a second radius of curvature of zero in the horizontaldirection.
 5. In the illuminated display device in accordance with claim4, wherein the light outlet surface (8) is shaped as a section of acylinder.
 6. In the illuminated display device in accordance with claim5, wherein the display lens (1) has a flange collar (6) on acircumference that abuts the display surface.
 7. In the illuminateddisplay device in accordance with claim 6, wherein a marker (10)identifying an installed position is formed on the flange collar (6). 8.In the illuminated display device in accordance with claim 7, whereinthe marker (10) is shaped as a section of a circle.
 9. In theilluminated display device in accordance with claim 1, wherein a radiusof curvature of the light outlet surface (8) is less in the horizontaldirection than in the vertical direction.
 10. In the illuminated displaydevice in accordance with claim 7, wherein the light outlet surface (8)is curved convexly toward an outside in the vertical direction and has asecond radius of curvature of zero in the horizontal direction.
 11. Inthe illuminated display device in accordance with claim 3, wherein thelight outlet surface (8) is shaped as a section of a cylinder.
 12. Inthe illuminated display device in accordance with claim 1, wherein thedisplay lens (1) has a flange collar (6) on a circumference that abutsthe display surface.